CN108693430A - A kind of segmented distribution network capacitance current test measuring circuit and its measurement method - Google Patents
A kind of segmented distribution network capacitance current test measuring circuit and its measurement method Download PDFInfo
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- CN108693430A CN108693430A CN201810328299.1A CN201810328299A CN108693430A CN 108693430 A CN108693430 A CN 108693430A CN 201810328299 A CN201810328299 A CN 201810328299A CN 108693430 A CN108693430 A CN 108693430A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention discloses a kind of segmented distribution network capacitance current test measuring circuit and its measurement methods comprising central processing unit;Signal generator;Open delta voltage measuring circuit;Zero-crossing detection circuit;Operational amplification circuit module;And DC bias circuit.It is PGA scalings and DAC dynamic regulations the present invention is based on the distribution network capacitance current test measuring circuit core of segmented measuring principle, to make full use of the dynamic range of ADC, and coordinate modified hardware zero cross detection circuit, to expand capacitance current measurement range, meet bulky capacitor current measurement demand;In addition measuring circuit also increases hardware over-voltage protection circuit, real-time judge distribution network system electric voltage exception, thus cut-out, the protection circuit in time in failure.
Description
[Technical field]
The present invention relates to power system measuring technical fields, and electricity is measured more particularly to a kind of segmented distribution network capacitance current test
Road and its measurement method.
[Background technology]
Early stage use capacity current measurement method be generally Single Phase Metal ground connection method, by by distribution network line artificially
Single phase grounding test is carried out, to directly measure the capacity current for flowing into the earth.Since this method needs to implement before operation
Complicated safety measure, and it is complicated for operation, it is also possible to the insulation for jeopardizing ungrounded phase insulation weakness, to cause two-phase
Strange land short circuit, therefore this method safety is low.Entire experiment process constitutes a threat to the safety of operating personnel and power grid, tries
The danger tested is big.Therefore, the shortcomings that capacity current not only can avoid direct method is measured using indirect measurement method, but also convenient for surveying
Amount.Common capacity current indirect measurement method is several under mainly having in engineering at present:
(1) Biased capacitor method:Principle is to add partially installing capacitor respectively in the three-phase of system, then by measuring respectively
Data solving equations are a kind of more commonly used methods in actually measuring to obtain the capacity current value of system.
(2) artificial neutral point's method:Direct-to-ground capacitance is accessed also in each phase of circuit, and manufactures an artificial neutral point
It measures.Its measurement accuracy it is higher and access direct-to-ground capacitance it is smaller, it is small to system shock therefore to be widely adopted.The method
The shortcomings that mainly will produce larger measurement error when the direct-to-ground capacitance numerical value of selection access is improper, and be possible to occur
Negative opens the case where radical sign so that measuring work can not implement.
(3) the resonance method:It is to measure neutral point voltage curve using series resonance principal to calculate the direct-to-ground capacitance of power grid
Value.Its advantages of is simple easily realization.But the premise that uses of this method must be power grid degree of asymmetry is smaller or extinguishing arc
In the case of coil series and parallel compensated resistance.When resonance occurs for arc suppression coil and system direct-to-ground capacitance, neutral point of electric network voltage will
Larger displacement occurs, to be damaged to power grid and equipment, the more serious short circuit accident that may cause system.
(4) modal equation method is the inductance value by changing arc suppression coil, and arc suppression coil both end voltage is caused to change,
So that the electric current in arc suppression coil changes.By detecting voltage, current value and the phase angle difference corresponding to it, pass through
Solving equations calculate system capacity current over the ground.The disadvantages of this method is that when in use, power grid must have certain injustice
Weighing apparatus degree.
(5) impedance triangle method:It is similar with modal equation method, by changing the inductance value of arc suppression coil come computing system
Capacitive reactance.It is generally used in the automatic tracking compensating device with loaded switch turn-adjusting arc-extinguishing winding.The measurement accuracy meeting of the method
It is influenced by tap setting and power network fluctuation.Meanwhile it is contemplated that arc suppression coil is non-thread when terminal voltage is smaller
Property distortion the problem of, and the method is only applicable to arc suppression coil series resistance earthed system.
(6) information synthetic method:It is so that neutral point voltage is reached maximum value by continuously adjusting arc suppression coil inductance value, by
Resonance principle is it is found that the induction reactance of arc suppression coil is equal to the capacitive reactance total over the ground of power grid at this time, and then can directly calculate system pair
Ground capacity current.The disadvantages of this method is can only could to be used in the case where power grid has certain degree of unbalancedness.
In recent years with the development of microcomputer technology and observation and control technology, injecting signal is in neutral point ungrounded electric network capacitive electricity
It is widely used in flow measurement and rapidly develops.The basic ideas of this method are opened from bus-bar potential transformer is secondary
Mouth triangle or arc suppression coil secondary side reload signal source by injecting the signal of specific frequency to system, and pass through analysis
Feedback signal is to calculate capacity current value in power distribution network.
(7) frequency variation method:The current signal of frequency conversion is injected into PT secondary side open-deltas side fourier algorithm to neutrality
The capacity current of point isolated neutral system measures, which can measure larger capacity current.But this method needs accurate note
Enter the frequency of signal, this signal is used for the range of the resonant frequency of measuring system.Usually only take certain two frequency in such a system
It puts to measure capacity current.If Frequency point selection is improper will to bring large error to measurement result, therefore this method is in reality
There is larger limitation on border in.
(8) power frequency method:A method of injecting 50Hz power frequency components into power distribution network, this method passes through to arc suppression coil electricity
The adjusting of inductance value, to measure the relationship between the voltage and electric current that feed back to, to achieve the purpose that tune automatically.This method
The shortcomings that be the offset voltage that can amplify isolated neutral system, to generate harmful effect to the insulation of equipment, simultaneously also
Earth protective devices at different levels may be caused to generate malfunction.In addition, external have document to propose that the signal of injection 50Hz can be in system
Neutral point generates a voltage, and voltage when this voltage and system normal operation is superimposed to generate unfavorable shadow to system
It rings.
[Invention content]
One of main object of the present invention is to provide a kind of segmented distribution network capacitance current test measuring circuit, be mainly used for small
The capacitance current of distribution network of current grounding system measures, and has high-resolution and larger measuring range, measurement result reliable and stable.
The present invention is achieved through the following technical solutions above-mentioned purpose:A kind of segmented distribution network capacitance current test measuring circuit and its
Measurement method comprising,
Central processing unit;
Signal generator conveys pulsed current signal to voltage transformer secondary side or open-delta;
Open delta voltage measuring circuit measures voltage transformer secondary side or the three-phase imbalance of open-delta return
Voltage signal, and it is uploaded to the central processing unit;
Zero-crossing detection circuit, detects the zero crossing of voltage transformer secondary side or open-delta and a pulse mode is touched
The injection for control pulsed current signal of sending out central processing unit described;
Operational amplification circuit module, the voltage that the central processing unit is uploaded according to the open delta voltage measuring circuit
Signal controls the enlargement ratio of the operational amplifying module;
DC bias circuit, the voltage signal that the central processing unit is uploaded according to the open delta voltage measuring circuit
Control the direct current biasing size of the DC bias circuit.
And the decompression filter circuit being connect with the amplification circuit module output end, the output of the decompression filter circuit
End is measurement result collection terminal.
Further, the three-phase imbalance voltage signal that the voltage transformer secondary side or open-delta return is divided into
Three tunnels, wherein the first via is input to the open delta voltage measuring circuit;Second tunnel is input to the zero-crossing examination electricity
Road;Third road is input to the control signal of the operational amplification circuit module and the DC bias circuit.
Further, the common input end on second road and the third road is provided with a 20kHz low-pass filters.
Further, further include that the sine wave being arranged in 20kHz first low pass filter outputs turns square wave module, output end
It is delivered to the central processing unit.
Further, the zero-crossing detection circuit includes 2500Hz second-order low-pass filters, third operational amplifier, ratio
Compared with device and monostable flipflop.
Further, times that the operational amplification circuit module includes several being arranged in parallel and amplification factor range is different
Number selection circuit and operational amplification circuit.
Further, every multiple selection circuit includes two resistance being arranged in series and by the centre
Manage device control folding and the control multiple selection circuit conducting photoelectricity coupling switch.
Further, the input terminal of the DC bias circuit is controlled by the central processing unit, is put with the operation
It is provided with photoelectric coupling switch on the circuit of big circuit module connection.
Another object of the present invention is to provide a kind of measurement method based on segmented distribution network capacitance current test measuring circuit,
It includes the following steps:
1) the square wave arteries and veins of a fixed pulse width is injected by signal generator to voltage transformer secondary side or open-delta
Rush current signal;
2) the three-phase imbalance voltage signal that voltage transformer returns is measured;
3) filtration treatment is overlapped to the voltage signal, and forms voltage change curve;
4) voltage change curve is divided into several sections of full curves;
5) according to every section of curve, adjustment controls the scaling and direct current biasing electricity of the operational amplification circuit module
The direct current biasing size on road carries out judging to find most in combination with the voltage signal that the open delta voltage measuring circuit returns
The scaling and direct current biasing size of the capacitance current measurement of suitable this section of curve;
6) zero crossing is found using zero-crossing detection circuit, and fixed pulse signal is sent out in the zero crossing, trigger institute
State the pulsed current signal injection in central processing unit interrupt step 1;
7) step 5-6 is repeated, until completing the measurement of entire voltage change curve.
Further, in step 5, the method for adjustment of the scaling and direct current biasing size is, when certain section of curve
When voltage signal is negative value, then it is set to become positive number by increasing direct current biasing;When the voltage signal of certain section of curve is attached positioned at 0
Closely, then it is made to be located within the scope of the intermediate settings of measuring range as possible by increasing direct current biasing and carrying out operation amplifier;When certain
When the voltage signal of section curve is more than range, then by reducing direct current biasing size and scaling, measuring range is located at
Intermediate settings within the scope of.
Compared with prior art, a kind of segmented distribution network capacitance current test measuring circuit and its measurement method of the invention is beneficial
Effect is:1) segmented measuring principle is used, improves the resolution ratio and capacitance current measurement amount of ADC Analog-digital Converters indirectly
Journey, segmented measuring principle core uses operational amplifier combination DAC direct current biasing dynamic regulation modes, according to neutral point voltage
And capacitance both end voltage after impulses injection for the first time, the scaling and DAC direct current biasing sizes of operational amplifier are adjusted, and
Entire change curve is divided into multiterminal full curve, and by injected pulse electric current repeatedly, injection every time measures one section of side
Formula completes entire curved measurement, to improve the resolution ratio and capacitance current measurement range of ADC analog-digital converters;
2) when due to power distribution network normal operation, it will usually have three-phase imbalance voltage, voltage usually within the scope of 0~5V,
And change as power distribution network loads, three-phase imbalance voltage has certain fluctuation, certainly will be had an impact to injected pulse signal, because
This measuring circuit uses the hardware zero cross detection circuit for turning square wave based on sine wave, is not necessarily to CPU software intervention, monitoring is sinusoidal in real time
Wave signal zero-crossing, pulse signal injection are uneven to reduce neutral point three-phase by the way of the injection of high-precision zero cross fired
Interference of the weighing apparatus voltage to measurement and signal acquisition ensures multiple pulses injection, the consistency of segment data acquisition;
3) hardware zero cross detection circuit core is using comparator and monostable trigger chip, monostable after reaching zero crossing
Flip chip sends out fixed pulse signal, and triggers CPU and interrupt control pulsed current signal injection, and improve measurement result can
By property and precision;
4) range of ADC dynamic regulations is made full use of, it is succinct that ADC resolution ratio and measurement accuracy are provided, to improve capacitance
Current measurement precision and range.
[Description of the drawings]
Fig. 1 is the principle framework structural schematic diagram of the embodiment of the present invention;
Fig. 2, which connects for split shed triangular voltages measuring circuit of the embodiment of the present invention with the circuit of 20kHz low-pass filters, to be shown
It is intended to;
Fig. 3, which connect for operational amplification circuit module in the embodiment of the present invention with the circuit of DC bias circuit dynamic regulation, to be shown
It is intended to;
Fig. 4 is the circuit connection diagram of zero-crossing detection circuit in the embodiment of the present invention.
[Specific implementation mode]
Embodiment:
Fig. 1-Fig. 4 is please referred to, the present embodiment is segmented distribution network capacitance current test measuring circuit comprising,
Central processor CPU;
Signal generator conveys pulsed current signal to voltage transformer secondary side or open-delta;
The three-phase that open delta voltage measuring circuit IC2, measurement voltage transformer secondary side or open-delta return is not
Balanced voltage signal, and it is uploaded to the central processor CPU;
Zero-crossing detection circuit, detect the zero crossing of voltage transformer secondary side or open-delta and be uploaded to it is described in
Central processor CPU ensures that pulsed current signal injection length keeps absolute synchronization with zero crossing;
Operational amplification circuit module, the central processor CPU are uploaded according to the open delta voltage measuring circuit IC2
Voltage signal control the enlargement ratio of described amplification module IC7-10, IC13;
DC bias circuit IC13, the central processor CPU are uploaded according to the open delta voltage measuring circuit IC2
Voltage signal control the direct current biasing size of the DC bias circuit IC13;
And the decompression filter circuit IC6 being connect with the amplification circuit module IC3 output ends, the decompression filter circuit
The output end of IC6 is measurement result collection terminal.
The three-phase imbalance voltage signal that voltage transformer secondary side or open-delta return is divided into three tunnels, wherein the
It is input to open delta voltage measuring circuit IC2 all the way;Second tunnel is input to the zero-crossing detection circuit;Third road is input to
The control signal of the operational amplification circuit module and the DC bias circuit.On second road and the third road
Common input end is provided with a 20kHz low-pass filters.The 20kHz low-pass filters are mainly by the first operational amplifier IC4
It is constituted with second operational amplifier IC5.
The input terminal of open delta voltage measuring circuit IC2 is provided with divider resistance R58, the R50 being arranged in series, partial pressure electricity
Setting is improved two diode Q4 being arranged in series of system pressure resistance performance between resistance R58 and divider resistance R50.Distribution is neutral
Point three-phase imbalance voltage signal is input to open delta electricity by divider resistance R58, series diode Q4, divider resistance R50
1 foot of measuring circuit IC2, the voltage signal of measurement is pressed to be input in the central processor CPU.
The present embodiment segmented distribution network capacitance current test measuring circuit further includes being arranged in 20kHz first low pass filter outputs
Sine wave turns square wave module I C12, and output end is delivered to the central processor CPU.
The zero-crossing detection circuit includes that 2500Hz second-order low-pass filters (including IC1A and IC1B), third operation are put
Big device IC2A, comparator IC3A and monostable flipflop IC4A.
Neutral point three-phase imbalance voltage is input to sine wave turns square wave module I C12 1 after 20kHz low-pass filters
VIN feet in foot i.e. figure, since different power distribution network three-phase imbalance voltage change amplitudes are larger, in order to ensure that zero crossing is examined
The Stability and veracity of survey first passes around 2500Hz second-order low-pass filters, then through the big ratios of third operational amplifier IC2A
Example amplification, is input to 3 foot of reverse input end of comparator IC3A, through comparing output to 4 feet of monostable flipflop IC4A, and leads to
The stable 2.2ms pulses of 6 feet output are crossed to central processor CPU Edge check input pin, and pass through central processor CPU pair
The interruption answered controls the injection moment of pulsed current signal.
The operational amplification circuit module includes multiple selection electricity several being arranged in parallel and that amplification factor range is different
Road IC7-IC10 and operational amplification circuit IC3.Every multiple selection circuit includes two resistance R12, R13 being arranged in series
(or R20, R21 or R22, R23 or R24, R25), and controlled described times of open and close and control by the central processor CPU
The photoelectricity coupling switch of number selection circuit conducting.
The input terminal of the DC bias circuit IC13 is controlled by the central processor CPU, with the operation amplifier
It is provided with photoelectric coupling switch IC11 on the circuit of circuit module connection.
The present embodiment further includes a kind of measurement method based on segmented distribution network capacitance current test measuring circuit comprising following
Step:
1) the square wave arteries and veins of a fixed pulse width is injected by signal generator to voltage transformer secondary side or open-delta
Rush current signal;
2) the three-phase imbalance voltage signal that voltage transformer returns is measured by open delta voltage measuring circuit IC2,
And it is uploaded to central processor CPU;
3) voltage signal received is overlapped filtration treatment by central processor CPU, that is, filters out mutual induction of voltage
Device once surveys the unbalance voltage of return, then forms voltage change curve;
4) voltage change curve is divided into several sections of full curves;
5) central processing unit is according to every section of curve, adjustment control the operational amplification circuit module scaling and
The direct current biasing size of the DC bias circuit IC13 is returned in combination with the open delta voltage measuring circuit IC2
Voltage signal carries out judging to find the scaling and direct current biasing size of the capacitance current measurement of most suitable this section of curve;When certain
When the voltage signal of section curve is negative value, then it is set to become positive number by increasing direct current biasing;If when the voltage letter of certain section of curve
Number it is located near 0, such as 0.3V, due to close to 0 point, be easy to causeing drift to generate larger measurement error, then passes through increase
Direct current biasing and progress operation amplifier, make it be located within the scope of the intermediate settings of measuring range as possible, to improve measurement accuracy;
When the voltage signal of certain section of curve is more than range, then by reducing direct current biasing size and scaling, measurement is located at
Within the scope of the intermediate settings of range;
6) zero crossing is found using zero-crossing detection circuit, and fixed pulse signal is sent out in the zero crossing, trigger institute
State the pulsed current signal injection in central processor CPU interrupt step 1;
7) step 5-6 is repeated, until completing the measurement of entire voltage change curve.
A kind of distribution network capacitance current test measuring circuit based on segmented measuring principle of the present embodiment, is mainly used for low current and connects
The capacitance current of distribution network of ground system measures, and the distribution network capacitance current test measuring circuit core based on segmented measuring principle is PGA
(operational amplifying module) and DAC dynamic regulations (DC bias circuit) are scaled, to make full use of the dynamic range of ADC, and is matched
It closes modified hardware zero cross detection circuit and meets bulky capacitor current measurement demand to expand capacitance current measurement range;In addition
Measuring circuit also increases hardware over-voltage protection circuit, real-time judge distribution network system electric voltage exception, to be cut in time in failure
Disconnected, protection circuit.
Traditional capacitance current measurement circuit is based on fixed frequency, frequency sweep and alien frequencies principle, the electric capacity measuring upper limit and most very much not surpasses
200uF is crossed, with the continuous expansion of city size, power distribution network scale constantly expands, to cause capacitance current to sharply increase,
Certain overhead transmission lines or heavy duty region, capacitance up to 300~400uF, so traditional capacitance current measuring method is not
Real needs can be met.Distribution network capacitance current test measuring circuit based on segmented measuring principle utilizes the external PT methods of neutral point, profit
With inverse-excitation type switch power-supply principle, fixed pulse width pulsed current signal, acquisition capacitance both end voltage variation are injected in PT low-pressure sides
Slope of a curve, this slope size are in inversely prroportional relationship with capacitance current size;Due to different power distribution network capacitance size difference
It is larger, so capacitance both end voltage change curve slope difference is larger, so the distribution capacitance electricity based on segmented measuring principle
Flow measurement circuitry capacitance both end voltage change curve slope size after impulses injection according to power network neutral point voltage and for the first time,
Automatic decision and adjustment PGA scalings and DAC direct current biasing sizes, the entire change curve data of piecewise acquisition, fully profit
With ADC dynamic ranges, ADC resolution ratio and measurement accuracy are improved indirectly, to improve capacitance current measurement precision and range.
The advantageous effect of the present embodiment segmented distribution network capacitance current test measuring circuit and its measurement method is:
1) segmented measuring principle is used, improves the resolution ratio and capacitance current measurement amount of ADC Analog-digital Converters indirectly
Journey, segmented measuring principle core uses operational amplifier combination DAC direct current biasing dynamic regulation modes, according to neutral point voltage
And capacitance both end voltage after impulses injection for the first time, the scaling and DAC direct current biasing sizes of operational amplifier are adjusted, and
Entire change curve is divided into multiterminal full curve, and by injected pulse electric current repeatedly, injection every time measures one section of side
Formula completes entire curved measurement, to improve the resolution ratio and capacitance current measurement range of ADC analog-digital converters;
2) when due to power distribution network normal operation, it will usually have three-phase imbalance voltage, voltage usually within the scope of 0~5V,
And change as power distribution network loads, three-phase imbalance voltage has certain fluctuation, certainly will be had an impact to injected pulse signal, because
This measuring circuit uses the hardware zero cross detection circuit for turning square wave based on sine wave, is not necessarily to CPU software intervention, monitoring is sinusoidal in real time
Wave signal zero-crossing, pulse signal injection are uneven to reduce neutral point three-phase by the way of the injection of high-precision zero cross fired
Interference of the weighing apparatus voltage to measurement and signal acquisition ensures multiple pulses injection, the consistency of segment data acquisition;
3) hardware zero cross detection circuit core is using comparator and monostable trigger chip, monostable after reaching zero crossing
Flip chip sends out fixed pulse signal, and triggers CPU and interrupt control pulsed current signal injection, and improve measurement result can
By property and precision;
4) range of ADC dynamic regulations is made full use of, it is succinct that ADC resolution ratio and measurement accuracy are provided, to improve capacitance
Current measurement precision and range.
Above-described is only some embodiments of the present invention.For those of ordinary skill in the art, not
Under the premise of being detached from the invention design, various modifications and improvements can be made, these belong to the protection model of the present invention
It encloses.
Claims (10)
1. a kind of segmented distribution network capacitance current test measuring circuit, it is characterised in that:It includes,
Central processing unit;
Signal generator conveys pulsed current signal to voltage transformer secondary side or open-delta;
Open delta voltage measuring circuit measures voltage transformer secondary side or the three-phase imbalance voltage of open-delta return
Signal, and it is uploaded to the central processing unit;
Zero-crossing detection circuit, detects the zero crossing of voltage transformer secondary side or open-delta and a pulse mode triggers institute
State the injection of central processing unit control pulsed current signal;
Operational amplification circuit module, the voltage signal that the central processing unit is uploaded according to the open delta voltage measuring circuit
Control the enlargement ratio of the operational amplifying module;
DC bias circuit, the central processing unit are controlled according to the voltage signal that the open delta voltage measuring circuit uploads
The direct current biasing size of the DC bias circuit.
And the decompression filter circuit being connect with the amplification circuit module output end, the output end of the decompression filter circuit are
For measurement result collection terminal.
2. segmented distribution network capacitance current test measuring circuit as described in claim 1, it is characterised in that:The voltage transformer two
The three-phase imbalance voltage signal that secondary side or open-delta return is divided into three tunnels, wherein the first via is input to the opening three
Angle voltage measuring circuit;Second tunnel is input to the zero-crossing detection circuit;Third road is input to the operational amplification circuit mould
The control signal of block and the DC bias circuit.
3. segmented distribution network capacitance current test measuring circuit as claimed in claim 2, it is characterised in that:In second road and institute
The common input end for stating third road is provided with a 20kHz low-pass filters.
4. segmented distribution network capacitance current test measuring circuit as claimed in claim 3, it is characterised in that:Further include that setting exists
The sine wave of 20kHz first low pass filter outputs turns square wave module, and output end is delivered to the central processing unit.
5. segmented distribution network capacitance current test measuring circuit as described in claim 1, it is characterised in that:The zero-crossing examination electricity
Road includes 2500Hz second-order low-pass filters, third operational amplifier, comparator and monostable flipflop.
6. segmented distribution network capacitance current test measuring circuit as described in claim 1, it is characterised in that:The operational amplification circuit
Module includes multiple selection circuits several being arranged in parallel and that amplification factor range is different and operational amplification circuit.
7. segmented distribution network capacitance current test measuring circuit as claimed in claim 6, it is characterised in that:Every multiple selection
Circuit includes two resistance being arranged in series and is controlled the open and close and control multiple selection electricity by the central processing unit
The photoelectricity coupling switch of road conducting.
8. segmented distribution network capacitance current test measuring circuit as described in claim 1, it is characterised in that:The DC bias circuit
Input terminal controlled by the central processing unit, be provided with photoelectricity coupling on the circuit being connected to the operational amplification circuit module
Combination switch.
9. a kind of measurement method of segmented distribution network capacitance current test measuring circuit as described in claim 1, it is characterised in that:Its
Include the following steps:
1) the square-wave pulse electricity of a fixed pulse width is injected by signal generator to voltage transformer secondary side or open-delta
Flow signal;
2) the three-phase imbalance voltage signal that voltage transformer returns is measured;
3) filtration treatment is overlapped to the voltage signal, and forms voltage change curve;
4) voltage change curve is divided into several sections of full curves;
5) according to every section of curve, the scaling and the DC bias circuit for controlling the operational amplification circuit module are adjusted
Direct current biasing size carries out judging to find most suitable in combination with the voltage signal that the open delta voltage measuring circuit returns
The scaling and direct current biasing size of the capacitance current measurement of this section of curve;
6) zero crossing is found using zero-crossing detection circuit, and fixed pulse signal is sent out in the zero crossing, during triggering is described
Pulsed current signal injection in central processor interrupt step 1;
7) step 5-6 is repeated, until completing the measurement of entire voltage change curve.
10. the measurement method of segmented distribution network capacitance current test measuring circuit as claimed in claim 9, it is characterised in that:Step 5
In, the method for adjustment of the scaling and direct current biasing size is when the voltage signal of certain section of curve is negative value, then to pass through
Increasing direct current biasing makes it become positive number;When certain section of curve voltage signal be located at zero near, then by increase direct current biasing and
Operation amplifier is carried out, it is made to be located within the scope of the intermediate settings of measuring range as possible;When the voltage signal of certain section of curve is more than amount
Cheng Shi is located at then by reducing direct current biasing size and scaling within the scope of the intermediate settings of measuring range.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110687343A (en) * | 2019-10-22 | 2020-01-14 | 阳光电源股份有限公司 | Leakage current detection method and circuit |
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